1,2,3,5,6,7,4,8-hexathiadiphosphocane-4,8-dithioxo-4,8-dithiolic acid and its salts



United States Patent 3,533,736 1,2,3,5,6,7,4,8-HEXATHIADIPHOSPHOCANE-4,8-DI- THIOX0-4,8-DITHIOLIC ACID AND ITS SALTS Herbert W. Roesky, Gottingen, Germany, assignor to E. I. du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware No Drawing. Filed Aug. 3, 1966, Ser. No. 569,809 Int. Cl. C0111 25/28 US. Cl. 23106 9 Claims ABSTRACT OF THE DISCLOSURE Described and claimed are 1,2,3,5,6,7,4,8-hexathiadiphosphocane-4,8-dithioxo-4,S-dithiolic acid and its salts. These novel compounds are useful chemical reducing agents.

Field of the invention This invention relates to a new inorganic acid and its salts and to their preparation.

Details of the invention The novel compounds of this invention are the acid H P S and its salts. These compounds have the formula M +(P S where M is any cation, i.e., hydrogen, a metal, NH or a loweralkyl or phenyl-substituted ammonium, arsonium, or phosphonium ion, and m is the valence of M. When In is an odd number, i.e., l or 3, a:2 and b=m. When m is an even number, i.e., 2 or 4, a=l and The alkali metal salts of this invention are prepared by the reaction of an alkali metal azide with P 8 in the presence of the dimethyl ether of ethylene glycol. By alkali metal is meant Li, Na, K, Rb, Cs, or Fr. The reaction proceeds at temperatures in the range from 0 to 100 C. Pressure is not a critical factor in the process and ambient pressures are satisfactory.

The molar ratio in which the alkali metal azide and P 8 are brought together in carrying out the reaction may be varied Widely, i.e., from 1:20 to :1. Molar ratios in the range of 1:2 to 2:1 are preferred.

The free acid H P S is obtained by the reaction of an alkali metal salt prepared as described above, with a cation-exchange resin in acid form. Other salts are prepared by metathesis.

In the compounds of this invention, the divalent P 5 anion is considered to have the structure and is referred to as the 1,2,3,5, 6,7,4,S-hexathiadiphosphocane-4,8-dithioxo-4,8-dithiolate dianion.

The products of this invention are all useful as chemical reducing agents. Thus, in neutral or alkaline systems they reduce permanganate to MnO and in acid systems they reduce permanganate to manganous ion. Specifically, an aqueous solution of disodium 1,2,3,5,6,7,4,8-hexathiadiphosphocane-4,8-dithioxo-4,S-dithiolate decolorizes an aqueous solution of potassium permanganate. The free acid and the soluble salts of this invention are also useful 3,533,736 Patented Oct. 13, 1970 for removing large cations from solution as shown in Example 2 below.

Specific embodiments of the invention In the following examples parts are by weight unless otherwise noted.

EXAMPLE 1 In a glass reactor a mixture of 3.9 g. NaN 4.4 g. P 5 and 50 ml. of ethylene glycol dimethyl ether (glyme) was stirred under nitrogen. The exothermic reaction heated the mixture to 35 C. within 15 minutes. The reaction mixture was then heated an additional 15 minutes at 40' C., cooled to room temperature and filtered. Glyme was removed from the filtrate under reduced pressure leaving a colorless viscous liquid which was dissolve in water to obtain a solution of disodium l,2,3,5,6,7,4,8-hexathiadiphosphocane-4,8-dithioxo-4,S-dithiolate, Na P S EXAMPLE 2 The solution obtained in Example 1 was filtered to remove a trace of sulfur which separated. To the filtrate was added an aqueous solution of tetra-n-propylammonium bromide. The white solid which precipitated was collected by filtration and recrystallized from methanol to yield 0.8 g. of tetra-n-propylammonium 1,2,3,5,6,7,4,8- hexathiadiphosphocane-4,8-dithioxo-4,8-dithiolate in the form of colorles crystals which darkened slightly at 112-153 C. and melted with decomposition at 229- 230 C.

AnaIysis.CalCd. for C24H5 N2P2Sm (percent): C, 38.20; H, 7.42; N, 3.72; P, 8.22; S, 42.4. Found '(percent): C, 37.92; H, 7.56; N, 3.86; P, 8.34; S, 43.27.

When an aqueous solution of Na P S obtained as in Example 1, is passed through a column of cation-exchange resin in acid form and washed through with additional water, an aqueous solution of the free acid H P S 1,2,3,5,6,7,4,8-hexathiadiphosphocane 4,8 dithioXo-4,8-dithiolic acid, is obtained. The pure acid is isolated as a colorless liquid by removal of water, for example, by evaporation or distillation.

When tetramethylammonium chloride, tetraethylammonium bromide, tetra-n-butylammonium chloride, tetraphenylarsonium chloride, and methyl triphenylphosphonium bromide are substituted for tetra-n-propylammonium bromide in the procedure of Example 2, the corresponding tetramethylammonium, tetraethylammonium, tetra-n-butylammoniu-m, tertaphenylarsonium, and methyl triphenylphosphonium 1,2,3,5,6,7,4,8-hexathiadiphosphocane-4,8-dithioxo-4,8-dithiolates are obtained as colorless crystalline solids.

When an aqueous solution of the free acid H P S 1,2,3,5,6,7,4,8 hexathiadiphosphocane 4,8 dithioxo- 4,8-dithiolic acid, reacts with the oxide or hydroxide of any metal, the corresponding metal salt is obtained. Thus, calcium oxide yields calcium 1,2,3,5,6,7,4,8-hexathiadiphosphocane-4,8-dithioxo-4,8-dithiolate, barium hydroxide yields barium l,2,3,5,6,7,4,8 hexathiadiphosphocanet,8- diothioxo-4,8-dithiolate, and zinc oxide yields zinc 1,2,3,5, 6,7,4,8 hexathiodiphosphocane 4,8 dithioxo-4,8-dithiolate. Operable metals include all elements with atomic numbers of 3, 4, 11-13, 19-32, 37-51, 55-84, 87-102, and above.

It is to be understood that the formula P 8 used here in refers to phosphorus pentasulfide, P 5 being the presently accepted formula for this compound rather than the older formula P S The foregoing detailed description has been given for clarity of understanding only an no unnecessary limita tions are to be understood therefrom. The invention is not limited to the exact details shown and described, for obvious modifications will be apparent to those skilled in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are as follows:

1. A compound of the formula 2. Compounds of claims 1 wherein M is selected from 20 the class consisting of hydrogen, metal, ammonium, loweralkyl and phenyl-substituted ammonium, arsonium and phosphonium ions.

3. Compounds of claim 1 wherein M is an alkali metal. 25

4. 1,2,3,5,6,7,4,8 hexathiadiphosphocane 4,8 dithioxo 4,8 dithiolic acid, the compound of claim 1 where M is hydrogen, 41:2, and 12:1.

5. Disodium 1,2,3,5,6,7,4,8 hexathiadiphosphocane- 4,8-dithioxo 4,8 dithiolate, the compound of claim 1 30 wherein M is sodium and a=2, and 17:1.

6. Tetra-n-propylammonium 1,2,3,5,6,7,4,8 hexathiadiphosphocane-4,8-dithioxo-4,8-dithiolate, the compound of claim 1 wherein M is tetra-n-propylammonium, a=2 and b=1.

7. Process for preparing compounds of claim 1 wherein M is an alkali metal cation which comprises reacting an alkali metal azide with P 8 in the presence of the dimethyl ether of ethylene glycol at 0 to 100 C.

8. Process of claim 7 in which the reaction is effected in a temperature range of from 0 to 100 C. and in a mole ratio of azide to P 5 of 1:20 to 20:1.

9. Process for preparing the acid of claim 4 which comprises contacting a solution of an alkali metal salt of claim 3 with an ion-exchange resin in its acidic form.

References Cited UNITED STATES PATENTS 3,197,404 7/1965 Berger et al. 252-400 2,744,083 5/1956 Moody et al 252-400 2,742,431 4/1956 Bishop 252400 OTHER REFERENCES Mosurski, Synthesis of Inhibitors and Additives for Lubricating Oils, Chem. Abs., vol. 52, No. 7675(a), 1958.

LELAND A. SEBASTIAN, Primary Examiner US. Cl. X.R. 

